Metal-insulator-metal (MIM) capacitors are well known. They are typically formed within the interconnect layers of an integrated circuit by depositing a metallic bottom plate, depositing a capacitor dielectric and then depositing, patterning and etching a metallic top plate. Typically to save cost and processing steps the top or bottom plate of the MIM capacitor may be formed using one of the layers of interconnect. For high precision MIM capacitors, however, the top and bottom plates are typically formed using separate metallic layers such as TaN and are not formed using interconnect material.
Metal resistors also may be formed within the interconnect layers of an integrated circuit. In some instances when both a MIM capacitor and a metal resistor are required, one of the plates of the MIM capacitor may be formed using an interconnect layer and the the other MIM capacitor plate material may also be used to form a metal resistor. While a process such as this may be used for many metal resistors, high precision metal resistors typically are formed of a very thin layer of a metallic material such as nichrome (NiCr), sichrome (SiCr), or TaSiN. These very thin metallic layers typically are too resistive to be used as a MIM capacitor plate.
In contrast to resistors located in the silicon substrate which suffer from relatively large parasitic capacitance to the substrate, metallic resistors have much less parasitic capacitance, since they are formed in the interconnect layers which are farther removed from the substrate. Hence, metallic resistors are preferred for high frequency RF applications.
A typical process flow for integrating a precision thin film metallic resistor into an integrated circuit manufacturing flow containing a high precision MIM capacitor may add three or four additional patterning steps and several thin film deposition and etch steps. One masking and etching step may be used to define the resistor which may be formed of a very thin film on the order of 1 nm to 10 nm to achieve high values of resistance. Since the resistor material is so thin, a special resistor contact pattern and etch may be required to form good electrical contact without damage to the thin resistor material. An alternative method that is used forms conductive etch stop landing pads over the heads of the thin film resistor which adds additional deposition, patterning, and etching steps. The addition of a high precision metal resistor to an integrated circuit manufacturing flow that also contains a high precision MIM capacitor typically adds significant additional cycletime and cost.